Fix for race condition where print preview hangs when attempting to print a PDF that hasn't loaded.

chrome/renderer/printing/print_web_view_helper.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/printing/print_web_view_helper.h"
 
 #include <string>
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
@@ skipping 802 matching lines @@
     return !IsScriptInitiatedPrintTooFrequent(frame);
   return true;
 }
 
 void PrintWebViewHelper::DidStartLoading() {
   is_loading_ = true;
 }
 
 void PrintWebViewHelper::DidStopLoading() {
   is_loading_ = false;
-  ShowScriptedPrintPreview();
+  if (request_print_preview_closure_.is_null()) {
+    ShowScriptedPrintPreview();

[Vitaly Buka (NO REVIEWS), 2014/08/05 06:05:06]

please remove ShowScriptedPrintPreview() from here use
request_print_preview_closure_ to call it.

request_print_preview_closure_ -> on_stop_loading_closure_ ?

[ivandavid, 2014/08/05 19:30:17]

Done.

+  } else {
+    request_print_preview_closure_.Run();
+    request_print_preview_closure_.Reset();
+  }
 }
 
 // Prints |frame| which called window.print().
 void PrintWebViewHelper::PrintPage(blink::WebLocalFrame* frame,
                                    bool user_initiated) {
   DCHECK(frame);
 
   // Allow Prerendering to cancel this print request if necessary.
   if (prerender::PrerenderHelper::IsPrerendering(
           render_view()->GetMainRenderFrame())) {
@@ skipping 883 matching lines @@
             base::Bind(&PrintWebViewHelper::ShowScriptedPrintPreview,
                        weak_ptr_factory_.GetWeakPtr()));
       }
       IPC::SyncMessage* msg =
           new PrintHostMsg_SetupScriptedPrintPreview(routing_id());
       msg->EnableMessagePumping();
       Send(msg);
       is_scripted_preview_delayed_ = false;
       return;
     }
     case PRINT_PREVIEW_USER_INITIATED_ENTIRE_FRAME: {

[ivandavid, 2014/07/29 20:02:51]

I encountered a similar problem to the one described in the bug when I was
working on a browser test that was printing PDFs. When I ran the browser test,
print preview would hang and just say 'Loading Preview...'. After some
investigation, it seemed like the problem that RequestPrintPreview() would be
called after DidStartLoading(), but before DidStopLoading(). So I modified the
code to cause it to wait for DidStopLoading() to be called to actually call
RequestPrintPreview() with the correct parameters and it fixed my problem. I was
only able to replicate this bug with the case
|PRINT_PREVIEW_USER_INITIATED_ENTIRE_FRAME|, therefore, I put the code there.

[Vitaly Buka (NO REVIEWS), 2014/08/05 05:49:57]

My understanding is that it's by design.
is_loading_ should be checked only for scripted preview.

For user initiated preview of web page it should be called immediately.
Page could be loading continuously for significant time, still user may wish to
print already loaded content.

Still maybe it's OK to have this exception for plugins. 
So it needs GetPlugin() check here like in case above.

On 2014/07/29 20:02:51, ivandavid wrote:

[ivandavid, 2014/08/05 19:30:17]

Done.

+      // If |is_loading_| is true and the function proceeds, Print Preview will
+      // hang. Save |type| and call this function when DidStopLoading() is
+      // called, ie. right when |is_loading_| is set to false.
+      if (is_loading_) {
+        request_print_preview_closure_ =
+            base::Bind(&PrintWebViewHelper::RequestPrintPreview,
+                       base::Unretained(this),
+                       type);
+        return;
+      }
+
       break;
     }
     case PRINT_PREVIEW_USER_INITIATED_SELECTION: {
       DCHECK(has_selection);
       params.selection_only = has_selection;
       break;
     }
     case PRINT_PREVIEW_USER_INITIATED_CONTEXT_NODE: {
       params.webnode_only = true;
       break;
@@ skipping 293 matching lines @@
 }
 
 void PrintWebViewHelper::PrintPreviewContext::ClearContext() {
   prep_frame_view_.reset();
   metafile_.reset();
   pages_to_render_.clear();
   error_ = PREVIEW_ERROR_NONE;
 }
 
 }  // namespace printing